Various objects, including mineral resources such as iron ore and limestone, are conveyed by a conveyor belt. When being conveyed by the conveyor belt, the objects to be conveyed are fed onto an upper cover rubber of the conveyor belt from a hopper or another conveyor belt. The fed objects to be conveyed are loaded on the upper cover rubber and conveyed in a travel direction of the conveyor belt. Here, the upper cover rubber is subject to wear as a result of the objects to be conveyed sliding on the upper cover rubber. When a conveyor belt with reduced tolerance strength due to wear caused by the objects to be conveyed is continuously used, the conveyor belt may suddenly sever, forcing the cessation of operations. For repairs, great amounts of time and costs are required. To prevent such problems, technologies for detecting the wear condition of conveyor belts are known (see for example Japanese Unexamined Patent Application Publication No. 2010-52927A).
According to the technology disclosed in Japanese Unexamined Patent Application Publication No. 2010-52927A, magnets are embedded in a conveyor belt, magnetism of the magnets is detected by a magnetism sensor, and the wear condition of the conveyor belt is detected on the basis of that measurement data. Although this method allows the wear condition of the range in which the magnets are embedded to be actually detected, the wear condition of the range in which magnets are not embedded cannot actually be detected, and can thus only be estimated.
Rather than being uniform across the entire range, the time-dependent wear condition of a conveyor belt varies. Wear can also arise locally for various reasons. Determining the wear condition of the range having the heaviest wear or an abnormal wear condition is important for preventing the conveyor belt from being severed. However, such wear conditions do not necessarily arise in the ranges where the magnets are embedded. Thus, to determine the wear condition of a desired range of a conveyor belt using the conventional method of embedding magnets in the conveyor belt, it is necessary to embed the magnets throughout a broad range, which is unrealistic. Therefore, means for accurately and efficiently determining the wear condition of a desired range of a conveyor belt has been required.